1. Field of the Invention
This invention relates to orthopaedic splint type devices used for the therapeutic treatment of instability and hyperextension of the finger joints.
2. Description of the Prior Art
Rheumatoid arthritis is an incurable disease which affects a large number of individuals to varying degrees. In severe cases, the disease is both painful and crippling. Various adaptive equipment and splints exist in the prior art to assist individuals in dealing with the effects of this disease.
When the hands become involved in the arthritic disease process, internal forces in the fingers change due to pain, inflammation and swelling. This creates an imbalance in forces which results in deformities. Specifically, as the tendons and ligaments around the joint become overstretched and the bone structure of the joint deteriorates due to the disease, the joints become very unstable in all directions through the full range of flexion and extension. Chronic pain and general muscle weakness exacerbate the problem of joint instability to the point of serious loss in function of the rheumatoid hand.
Joint instability in the lateral plane frequently results in loss of prehension, ulnar drift and other functional problems.
Joint instability in the flexion-extension plane often results in hyperextension of the finger joints resulting in a deformity called "swan-neck deformity". This condition is characterized by hyperextension of the interphalangeal joints of the finger in the dorsal direction (away from the palm of the hand) substantially more than the approximately 180.degree. extension found in the normal finger.
There are numerous types of finger splints and orthopaedic support devices available in the prior and existing art to prevent the fingers from hyperextending. The closest prior art known to applicant is set forth in the following U.S. Patent:
U.S. Pat. No. 3,170,460 - Stilson: "One-Piece Openwork Finger Splint", patent issued: Feb. 23, 1965. PA1 U.S. Pat. No. 4,270,528 - Hanson: "Finger Ring Splint", patent issued: June 2, 1981. PA1 U.S. Pat. No. 4,297,992 - LaRue, et al.: "Distal Joint Finger Splint", patent issued: Nov. 3, 1981. PA1 (a) They fail to stabilize the joint in the lateral plane; PA1 (b) They are bulky and uncomfortable to wear and abnormally abduct the fingers (spread the fingers apart); PA1 (c) Finger splints on adjacent fingers interfere with each other; PA1 (d) They are difficult or impossible for the wearer to adjust when the fingers expand and contract with changes in weather, activity and medical condition of the patient; and PA1 (e) They are aesthetically unattractive resulting in low patient compliance in the use of the splints.
Additional relevant art which may be prior or subsequent to applicant's invention, but which is approximately contemporaneous is shown in the following U.S. Patents:
Applicant is an Occupational Therapist who herself has lateral instability and hyperextension of the interphalangeal joints. As such, she has noted in herself and her patients that the finger splints commercially available in the prior art have the following objections to use:
The instant invention overcomes these problems and objections by making the splint from two custom fit elliptical rings lying in intersecting planes and with their major axes joined at an apex which, when worn, is positioned immediately under the finger joint. Use of custom fit elliptical rings permits an exact fit of the finger on each side of the interphalangeal joint. The exact fit of the finger and placement of the apex of the rings directly under the joint results in joint stabilization in the lateral plane at all times and through all degrees of flexion and extension.
Prior art does not provide lateral stabilization, but rather the distal phalanx remains unsupported in all positions except full extension. This result necessarily occurs in Hanson (see reference above) because the distal ring joins the proximal ring rearward of the joint and therefore must be large enough to provide clearance for the interphalangeal joint during flexion.
Additionally, elliptical proximal and distal rings permit the use of smaller, more malleable and more yieldable materials such as fine silver and gold to make finger splints which are small in size relative to the prior art, more comfortable to wear, more attractive and more easily adjustable, and are therefore of greater therapeutic value because the patient is more compliant in the use of the prescribed therapeutic (orthotic) device.